1. Field of the Invention
The present invention relates to a network of transceivers which monitor a defined geographic area for the receipt of transmissions indicative of emergency situations, and which relay an alarm signal to a central station for appropriate action. More particularly, the present invention is directed to an improved network of such transceivers wherein the location of the emergency situation is well defined when it is relayed to the central station.
2. Description of the Prior Art
Emergency transmitter systems are known in the art. U.S. Pat. No. 4,998,095, which issued to N. G. Shields on Mar. 5, 1991, describes an emergency transmitter system for individuals within a predetermined geographic area such as a campus, shopping mall, or stadium. A plurality of fixed transceivers at selected locations in the are monitor radio frequency emergency transmissions from portable transmitters. All transceivers that receive an emergency transmission produce a local alarm (strobe light, siren, or other audio alarm indicator) and transmit an alarm signal to a central station. The alarm signal includes the identity of the individual transmitter as well as the identity of the transceiver.
If an emergency transmission is received by more than one transceiver, each receiving transceiver will produce a local alarm and will transmit an alarm signal to the central station. Besides the disturbance factor of having many local alarms activated, security personal responding to the alarm are likely to be confused by the many activated alarms and therefore be less likely to locate the problem than if only the one closest transceiver was activated.
In the emergency transmitter system described in the Shields patent, transceiver locations are restricted to light poles and other similar structure where local electrical power is available. While battery operation might be considered, receipt of an emergency transmission by more than one transceiver, and the associated activation of the local alarms of each receiving transceiver, consumes additional battery life and makes battery operation less desirable.